Silver halide photographic materials currently on the market and methods for forming images using the same vary over a wide range and are used in various fields. Many of the halide compositions of silver halide emulsions used in these photographic materials, in particular those of shooting photographic materials, consist of silver bromoiodide that is mainly made up of silver bromide, for the purpose of attaining high sensitivity.
On the other hand, in products that are used in a market where there is strong demand for a large amount of prints to be finished and delivered in a short period of time, such as photographic materials for color papers, silver bromide or silver chlorobromide that is substantially free from silver iodide is used, in order to hasten the developing speed.
In recent years the demand for the improvement of rapid processibility of color papers has been increasingly strong and many studies thereof are under way. It is known that an increase in the silver chloride content of the silver halide emulsion to be used will greatly improve developing speed.
However, it is known that silver halide emulsions high in silver chloride content are attended with such defects that they hardly provide emulsions high in sensitivity and hard in gradation. Further the emulsions have a defect in reciprocity law failure. That is, the change of sensitivity and gradation due to a change in illuminance of exposure is great.
In order to overcome the above defects of silver halide emulsions high in silver chloride content, various techniques have been proposed.
JP-A ("JP-A" means unexamined published Japanese patent application) No. 26837/1989 discloses that a high-silver-chloride emulsion, whose grains have regions rich in silver bromide near the vertices gives high sensitivity and gradation and stable performance. JP-A No. 105940/1989 discloses that a high-silver-chloride emulsion having regions rich in silver bromide doped selectively with iridium constitutes an emulsion excellent in reciprocity response without damaging latent-image stability for a few hours after exposure.
Thereafter, the inventors have keenly continued the study for increasing the performance of high-silver-chloride emulsions. As a result, it has been found that the use of high-silver-chloride emulsions prepared in the above manner in a photographic material is attended with defects. The gradation becomes soft if the photographic material is exposed to light of a safelight before printing, and fogging easily occurs if pressure is exerted on the photographic material before processing. If such things take place, not the photographic material will lack handlability in a photofinishing lab, and the finished quality of the print will probably be deteriorated.